1. Field of the Invention
Various embodiments of the invention relate to the detection of errors in ultrasonic transit time measurements. More particularly, embodiments of the invention relate to establishing the delay times inherent in one or more transducer pairs used in an ultrasonic meter, and identification of when delay time errors have been measured inaccurately or have changed. Related embodiments are directed to the identification of mistakes in measured distance between transducer pairs in an ultrasonic meter.
2. Description of the Related Art
After hydrocarbons have been removed from the ground, the fluid stream (such as natural gas) is transported from place to place via pipelines. It is desirable to know with accuracy the amount of fluid flowing in the stream, and particular accuracy is demanded when the fluid is changing hands, or “custody transfer.” Even where custody transfer is not taking place, however, measurement accuracy is desirable.
Measurement of flow velocity and speed of sound in the ultrasonic meter, in order to determine the amount of fluid flow, depends on measured transit time or time of flight of the ultrasonic signals. A difficulty that arises in measuring precisely the time of flight for an ultrasonic signal is determining the actual time of flight as contrasted to a measured time of flight. The calculation of fluid flow velocity, as well as the speed of sound for the fluid, is based on the “actual” time of flight, which excludes delays from the electronics, matching layers and other factors.
Thus there exists a need for methods and systems that improve the accuracy of the actual time of flight measurements and identify the cause of inaccuracies in actual time of flight measurements.